Transient radiation myelopathy: spinal somatosensory evoked responses following incidental cord exposure during radiotherapy

On the significance of Lhermitte's sign in oncology

We present three cases of Lhermitte's sign out of twenty consecutive cases of epidural spinal cord compression due to metastatic cancer. The three patients were diagnosed with epidural thoracic compressions. The literature on Lhermitte's sign is reviewed with emphasis on the differential diagnosis of this symptom in oncological patients.

Long-term nervous system damage from radiation of the spinal cord: an electrophysiological study

A group of 13 patients suffering from Hodgkin's disease who had undergone chemotherapy and radiotherapy (above and below the diaphragm) approximately 10 years earlier was studied. The total chemotherapeutic dose was similar for all patients; the radiotherapy dose, however, was standard for 7 patients, while the other 6 received much higher dosages over limited regions of the spinal cord. Although most of these patients appeared normal both clinically and on magnetic resonance imaging, a neurophysiological study was performed to determine whether there was any involvement of the central or peripheral nervous system. Motor conduction velocity and sensory conduction velocity were measured in the lower limbs as well as spinal- and scalp-recorded somatosensory evoked potentials (SEPs) in response to stimulation of the posterior tibial and sural nerves at the ankle. In addition, motor evoked potentials were recorded from the upper and lower limbs during cortical stimulation. All neurophysiological data were normal in patients who had received a standard radiation dose, while most of those who had been exposed to higher doses showed altered cortical SEPs and a slowing of central conduction time (D10-P1). Thus even though they were asymptomatic, these patients appeared to have sustained CNS damage, mainly at the level of the spinal cord.

Radiation myelopathy: a review

Radiation myelopathy is a serious potential complication associated with radiation therapy to the spinal cord. Its exact cause is unknown. It represents a spectrum of syndromes, the most common of which are acute transient radiation myelopathy and chronic progressive radiation myelitis. A review of the literature indicates that cord damage is related to a number of controllable factors including dose fraction size, treatment time, total dose, length of cord irradiated, technical and clerical errors. Other less well understood factors that appear to contribute to the risk such as combined chemoradiotherapy effects and hyperthermia should also be recognized. A better awareness and understanding of these factors should ultimately lead to safer and more effective treatments.

The clinical role of somatosensory evoked potential studies: a critical appraisal

The clinical utility and limitations of somatosensory evoked potential (SEP) studies are reviewed. Somatosensory evoked potentials may help to identify a lesion in the sensory pathways, but do not indicate its nature. In multiple sclerosis subjects, the SEP findings may help to establish that there is a multiplicity of lesions, but multimodality evoked potential abnormalities may occur in other disorders. Somatosensory evoked potential abnormalities do not reflect either the severity or the prognosis of cervical spondylosis and do not reliably permit early recognition of the totality of traumatic cord lesions, while the role of SEPs in monitoring cord function intraoperatively awaits definition. Somatosensory evoked potentials do not reliably indicate the individual prognosis after severe head injury, and discrepancies in published findings suggest that their use in the evaluation of brain death is premature. In hereditary spinocerebellar degenerations, SEP abnormalities may reflect central or peripheral pathology. Somatosensory evoked potentials can be used to determine conduction velocity in peripheral nerves and to identify inaccessible proximal lesions of these nerves, but the findings may lead to misleading conclusions about brachial plexus lesions, especially if pre- and postganglionic lesions coexist.

Visual, cortical somatosensory and brainstem auditory evoked potentials following incidental irradiation of the rhombencephalon

Visual, cortical somatosensory and brainstem auditory evoked potentials were recorded before incidental irradiation of the rhombencephalon and at 11 weeks and eight months after completion of treatment. No patient experienced neurological symptoms during this period. No consistent changes in evoked potentials were found. The failure to demonstrate subclinical radiation-induced demyelination suggests either that the syndrome of early-delayed radiation rhombencephalopathy occurs in an idiosyncratic manner, or that any subclinical lesions are not detectable by serial evoked potential recordings.

Electrophysiologic evidence of subclinical injury to the posterior columns of the human spinal cord after therapeutic radiation

Spinal somatosensory conduction velocity (SSCV) was indirectly estimated from cerebral evoked potentials in 15 adults who had received therapeutic radiation (RT) (2000-4380 rad) to the thoracic spinal cord during treatment for lung cancer, and in 15 age-matched normal controls. Thirteen of the patients had also received 4400-5500 rad to the supraclavicular fossae. One-way impulse conduction time in the arm, estimated from F-wave latency, was prolonged in the patients as compared to controls (12.0 +/- 1.2 versus 10.4 +/- 1.0 msec; P less than 0.001) but conduction time in the leg was similar in the two groups (22.4 +/- 2.4 versus 22.0 +/- 2.5 msec; P less than 0.1). SSCV was significantly slower in the patient group (37.9 +/- 13.9 versus 54.5 +/- 12.9 m/sec; P less than 0.001) whereas supraspinal latency (cervical cord to cortex) was identical (5.5 +/- 0.9 versus 5.5 +/- 0.8 msec; P less than 0.1). SSCV in the patient group was not related to total RT dose (r = 0.15; P = 0.2), but was correlated with both treatment time and number of fractions (r = 0.49 and 0.43; P = 0.003 and 0.007, respectively). These findings suggest that RT may produce subclinical spinal cord dysfunction even at conventional dosage schedules, and that it may be possible physiologically to monitor the myelopathic effects of RT in individual patients.

Early-delayed radiation rhombencephalopathy

A 37-year-old woman developed an early-delayed rhombencephalopathy 7 weeks after completing a course of radiotherapy to a glomus jugulare tumour. The clinical features, comprising nystagmus, skew strabismus, unilateral facial weakness, dysarthria and ataxia, are compared with four previously reported patients with this syndrome.

Congenital mirror movements

In this report are described seven patients assessed clinically and neuropsychologically in whom mirror movements affecting predominantly the hands occurred as a congenital disorder. These mirror movements, representing a specific type of abnormal synkinesia, may arise as a hereditary condition, in the presence of a recognisable underlying neurological abnormality, and sporadically, and the seven patients provide more or less satisfactory examples of each of these three groups. Despite the apparent uniformity of the disorder, the heterogeneity and variability may be marked, examples in some of our patients including the pronounced increase in tone that developed with arm movement, and the capacity for modulation of the associated movement by alteration of neck position and bio-feedback. Various possible mechanisms are considered; these include impaired cerebral inhibition of unwanted movements, and functioning of abnormal motor pathways. Emphasis has been placed on the putative role of the direct, crossed corticomotoneurone pathways and on the unilateral and bilateral cerebral events that precede movement.